1. Field of the Invention
The present invention relates to a spindle apparatus for winding fibers and, more particularly, to a spindle apparatus of the type that is directly coupled to and driven by an electric motor. Still more particularly, the invention is concerned with a fiber winding spindle apparatus directly driven by an electric motor, which is improved to prevent lifting of rotary parts and suppress vertical oscillation of the rotary parts.
2. Description of the Prior Art
Japanese Patent Examined Publication No. 54-32864 and U.S. Pat. No. 1,840,642 disclose, respectively, a spindle apparatus in which a plurality of spindles are directly driven by independent electric motors, in contrast to conventional apparatus in which the spindles are driven by a motor through tapes. The direct-drive type apparatus is advantageous in that no substantial radial load is applied to each spindle bearing as compared with the tape-driven type apparatus in which the spindle bearings are radially loaded due to tension in the driving tapes. In addition, the direct-drive type apparatus suffers from reduced fluctuation in the rotational speed, so that a high fiber-winding speed can be attained.
Current spindle apparatus for winding fibers are required to operate a high speed of from 15,000 to 30,000 rpm or higher. With the conventional tape-driven type apparatus, it is extremely difficult to attain such a high operation speed because, at such a high operation speed, the driving tapes tend to slip on the surface of the spindle wharve. In addition, a difference in the operation speed tends to be caused between different spindles, so that the spindle apparatus as a whole cannot operate satisfactorily. The tape-driven type apparatus also tends to exhibit precessions of spindles due to large radial load applied to the spindle, with the result that the bearings are worn down rapidly and heat is generated in the bearings. In consequence, the life of the spindle apparatus is shortened and the levels of noise and vibration are increased during operation of the spindle apparatus.
In the prior art direct-drive type spinde apparatus, the rotary portions of the apparatus are allowed to freely move upwards to certain heights. Therefore, the rotary portions may oscillate vertically when the rotational speed of the spindle apparatus is increased or when any unbalance of rotating mass is caused due to unbalanced winding of fibers. The sole factor which can suppress the vertical oscillation of the rotary parts is the weight of the rotary parts. Therefore, once the vertical oscillation of the rotary parts has taken place, the insert bearing, particularly the pivot bearing of the foot step in the lower portion of the apparatus, tends to be damaged, resulting in a shortened life of the spindle apparatus.